The interplay between coupled degrees of freedom drives emergent phenomena such as ferroelectricity, multiferroicity, superconductivity, colossal magnetoresistance, and charge density waves. Advances in optical techniques now enable selective excitation of phonon modes, offering a pathway to manipulate other degrees of freedom, including orbitals and spin waves. However, a detailed understanding of how orbital and exchange interactions $J$ evolve under phonon excitation, and how this evolution modifies the spin wave, remains lacking. To address this gap, we investigate phonon-driven effects in the prototypical antiferromagnetic (AFM) oxide ${\mathrm{YCrO}}_3$, which exhibits contributions from all five partially occupied Cr $d$ orbitals. In the unperturbed ${\mathrm{YCrO}}_3$, the partially occupied orbitals, mediated by the ligand, have different overlap orientations, which induce competition between orbitals contributing to ferromagnetic (FM) and AFM interactions. Selective narrow- and finite-bandwidth phonon excitation perturbs the orbital overlaps and their relative contribution to FM and AFM interactions, lifts the degeneracies, renormalizes $J$'s, and significantly alters the spin waves. The renormalized $J$'s further modify the interatomic force constant and the phonons via a coupled spin-phonon Hamiltonian. Our quantitative analysis offers a deeper understanding of exchange pathways and spin dynamics under phonon excitations, opening opportunities for tailored magnetic functionalities in spintronics and quantum materials.

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• Antiferromagnetism
• Electronic structure
• Exchange interaction
• Magnons
• Phonons
• Spin dynamics
• Spin-phonon coupling
• Density functional theory
• Fourier transform infrared spectroscopy
• Green's function methods
• Spin wave theory
• Wannier function methods